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Message 7 of 7
Posted by member cracker too on Wednesday 20 July 2016

Thanks for that Simon have heard mixed "real world" reviews. brgds. Martin.

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Message 6 of 7
Posted by member John on Tuesday 19 July 2016

Galvanic Isolators. If your boat is connected to shore power a good idea. Your boat mains shore cable has a ground conductor and this also connects to your boat and battery ground . But so connected is the boat next to you. Due to various leakages and galvanic action his ground may not be the same as yours and this can create a current path looping round your stern gear (effectively well grounded in accordance with Simons recommendation!) through the sea water battery to his stern gear, up his ground wire, via shore power then down your ground wire so completing a circuit. And creating conditions for possible corrosion. The resulting ac/dc voltages and currents are usually very small, the actual amounts and causes varied - I have measured some 10-30mA and maybe 0.5 volts or so. But this is 24 hours a day and 365 days a year which soon adds up. There are several types of Galvanic isolator, one type used on boats typically comprising silicon diodes connected back to back and inserted in the mains ground wiring. Diodes can have a drop of some 1.25 volts or so before they conduct but as this is usually below any likely voltage it is sufficient to prevent any leakage current flow in the ground wire. . Your boat is of course is already fitted with an RCD circuit breaker. but the galvanic Isolator MUST also be of sufficient rating to safely carry any prospective fault current which may arise before a circuit trips, reflected in size and cost and there are safety standards for these. It is in your safety wiring. Easy to fit and several manufacturers supply these located by the usual internet search

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Message 5 of 7
Posted by member Simon Kidd on Tuesday 19 July 2016

Hi Martin. Galvanic Isolators? I'd be honest, the only time I tend to see them, there's clearly already been a corrosion problem and the isolator fitted as a skicking plaster. I have found that 12v current leaks are more destructive - though thats just an opinion following observations. Galvanic isolators are perhaps useful if you have a boat in a yard with a lot of welded going on locally - or of stories of corrosion issues (trippy electrics - RCD's etc). Best Regards Simon.

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Message 4 of 7
Posted by member cracker too on Monday 18 July 2016

Simon any observations on cathodic isolators? brgds. martin.

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Message 3 of 7
Posted by member John on Monday 11 July 2016

* Many years ago when my 32 (No.3) was delivered it had no shaft anodes. The original hull anodes were quite small and did not provide enough protection. A later image shows shaft anodes fitted (and a rope cutter). There were no further problems so probably a good idea. Perhaps you could grind one anode face down a little or roughen the inside of the anodes to create a tighter fit? Anodes may now be larger on later boats.

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Message 2 of 7
Posted by member Simon Kidd on Monday 11 July 2016

Hi Peter. I find shaft anodes are often fitted to many boats, but due to the rattle issues and drag etc, rarely to faster boats - they normally seem to be fitted as belt a braces on slow vessels and river boats (but I do see them now and again on faster craft - belt and braces is better that none at all). I see genuine cases of corroson to stern gear monthly - if not weekly, noramlly in the form of prop de-zincification (Manganese bronze is the common material - and really this is closer to brass, not bronze - so protection of the shafts and props is important in my opinion. Good protection is normally afforded by fittiing good quality shaft brushes within the engine / stern gear compartment, wired with high quality wire and fittings to the hull anodes. As low electrcial resistance is the key. I'm not a beleiver of Anodes only working when they can "see" sterngear etc, but a very good low resistance connection is essential. I normally check resistance with a simple muti meter as a basic check on the lowerest resistance scale with will often fine 0 ohms (now, there is clearly resistance, but low enough). I tend to see corrosion either where there are no anodes (far too common) or where there are at least a few ohns resistance in the cathodic circuit. It should be noted that I only ever get to se the visible corroion, i,e unless the prop is removed, I'll not get to see if crevice corrosion is present on teh shaft, though I do hear of this (also in stern glands etc). In terms of materials - Austinetic Stainless steel has been in use for many years - though a few cheaper types are out these - I'd think it unlikley Hardy fitted this stuff. Bare one last thing in mind, in some cases - I'll see corroion creeping in even with a good cathodic protection system - noramly due to an DC leak (poor bilge pump wiring etc) or AC - fault charger or immersion heater being the most common - so even a perfect system doesn't solve all issues. So - perhaps - if removing the shaft anodes, fit larger or additional hull anodes? Just my thoughts on the matter. I'm sure others will have more to add. Best Regards Simon.

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Message 1 of 7
Posted by member Peter Cox on Monday 11 July 2016

My twin-shaft Hardy 32 has developed a rattle from the port prop/shaft that only appears when the prop is rotating. I am hoping, and based on past experience, that it's the shaft anode coming loose again. So far, I've had shaft anodes come loose or fall off completely several times, despite using Loctite-type fluid and hammering the anode to fit the shaft more tightly. An expensive liftout just to tighten a few bolts is very uneconomic. My previous twin shaft Hardy 27 had no shaft anodes at all and never had any problems (but incidentally I had to retrofit some rudder anodes after getting some problems on the rudders). My question to HOC members, especially the ex-Hardy staff, is whether shaft anodes were factory fitted and whether they are required at all? The pear hull anodes are close to the sterngear and in direct line of sight. Having said that, the shaft anodes do wear, so are doing their job, but if they are merely taking some of the load off the pear anodes that could easily cope on their own, I'd like to get rid of the shaft anodes. I have read one opinion that shaft anodes are a throwback to the days of non S/S shafts and pure brass/bronze props and are therefore no longer necessary, but are a good earner for anode makers, chandleries and boatyards.

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